1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display module that provides reliable and efficient module assembly.
2. Discussion of the Related Art
A cathode ray tube (CRT) is often used in TVs and monitors as a measuring instrument and an information terminal. However, due to its weight and size, the CRT cannot meet the requirements of the current trend of thin profile and light weight. Since the CRT cannot satisfy the above requirements, the CRT is being replaced with a Liquid Crystal Display (LCD) device that uses an electric field optical effect, a Plasma Display Panel (PDP) device that uses discharge, and an Electro Luminescent Display (ELD) device that uses an electric field luminescent effect. Among these display devices, the LCD device has been extensively researched and developed.
The LCD device has several advantages including small size, a light weight, and low power consumption. The LCD device is often used now as a monitor for a laptop computer, a monitor for a desktop computer, and a large-sized display device. Accordingly, demand for the LCD device has continuously increased. Most LCD devices are light-receiving devices that display an image by adjusting the amount of light supplied from the outside. Thus, this type of LCD device requires a separate light source for irradiating light on an LCD panel ( i.e., a back light unit). Back light units are divided according to the positions of lamp units, into an edge-type back light unit and a right below-type back light unit.
An Electro Luminescence (EL), a Light Emitting Diode (LED), a Cold Cathode Fluorescent Lamp (CCFL), or a Hot Cathode Fluorescent Lamp (HCFL) is used as the light source in LCD devices. Particularly, the CCFL, which has a long lifespan, low power consumption, and a thin profile, is mainly used in a large-sized color TFT-LCD.
FIG. 1 is a schematic exploded perspective view of a related art liquid crystal display device. As shown in FIG. 1, the related art liquid crystal display device includes a liquid crystal display panel 30 displaying an image, a fluorescent lamp 31 generating light, a lamp housing 32 formed in a U shape for surrounding the fluorescent lamp 31, a diffusion sheet 35, a first prism sheet 37, a second prism sheet 36, a protection sheet 38, a light guide panel 33, and a reflection plate 34.
The related art liquid crystal display device further includes a main support 39 for receiving the liquid crystal display panel 30 and a back light unit . Here, the fluorescent lamp 31, the lamp housing 32, the diffusion sheet 35, the first prism sheet 37, the second prism sheet 36, the protection sheet 38, the light guide panel 33, and the reflection plate 34 form the back light unit. The back light unit serves as a light source for the liquid crystal display panel 30 by irradiating light onto a display region (A) of the liquid crystal display panel 30. Although not shown in the drawings, the display region (A) of the liquid crystal display panel 30 includes two transparent substrates. Each transparent substrate has a polarization plate attached to the outer surface thereof, and a liquid crystal layer is formed between the inner surfaces of the two transparent substrates. The related art liquid crystal display device further includes a driving circuit 40 for driving the display region (A).
The back light unit is operated by the following method. When the fluorescent lamp 31 installed at one end of the light guide panel 33 is turned on, light generated from the fluorescent lamp 31 is reflected by the lamp housing 32. Reflected light is transferred to the other end of the light guide panel 33 (opposite side to the fluorescent lamp 31) through the cross section of the light guide panel 33. Accordingly, the light is spread over the surface of the light guide panel 33, and the spread light is irradiated onto the display region (A) by the diffusion sheet 35.
In the above related art liquid crystal display device, TFTs formed on the liquid crystal display panel 30 control pixels according to the signal of the driving circuit. The pixels selectively pass the light irradiated onto the display region (A) to display an image on the display region (A) of the liquid crystal panel 30. Hereinafter, a related art liquid crystal display module will be described with references to FIGS. 2 and 3.
FIG. 2 is a perspective view of the related art liquid crystal display module, and FIG. 3 is a sectional view taken along the line II-II′ of FIG. 2. As shown in FIGS. 2 and 3, the related art liquid crystal display module includes a main support 2, a back light unit 26 and a liquid crystal display panel 10 stacked next to the main support 2, a bottom cover 14 surrounding a first side surface and the bottom surface of the main support 2, and a top case 16 surrounding the edge of the liquid crystal display panel 10 and the side of the bottom cover 14.
Here, the main support 2 is a molded structure and has the stepped shape inner wall. The back light unit 26 is installed at the lowermost portion of the main support 2, and the liquid crystal display panel 10 is installed on the back light unit 26. The liquid crystal display panel 10 includes a lower substrate 10b on which TFTs are mounted, and an upper substrate 10a on which color filters are formed.
A liquid crystal is injected into a space between the lower substrate 10b and the upper substrate 10a. Polarization plates 22 and 24 are installed on the lower and upper surfaces of the liquid crystal display panel 10. The lower polarization plate 22 installed on the lower surface of the liquid crystal display panel 10 polarizes light supplied from the back light unit, then supplies the polarized light to the liquid crystal display panel 10. The upper polarization plate 24 installed on the upper surface of the liquid crystal display panel 10 polarizes light supplied from the liquid crystal display panel 10, and discharges the polarized light to the outside.
The bottom cover 14 surrounds the first side surface and the bottom surface of the main support 2. The top case 16 surrounds the upper portion and the portion of first side surface of the main support 2 to fix the main support 2 and the liquid crystal panel 10. The back light unit 26 includes a lamp housing 18 on which a light source 20 is mounted, a light guide panel 6 for converting light incident from the light source 20 into surface light, optical sheets 12 attached to the front surface of the light guide panel 6 to increase the efficiency of light incident on the liquid crystal display panel 10, and a reflection plate 4 attached to the rear surface of the light guide panel 6 for reflecting the light emitted from the rear surface of the light guide panel 6 towards the liquid crystal panel 10.
The light source 20 supplies designated light to the light guide panel 6 in response to power supplied from an external power source. Here, light emitted from the light source 20 in the direction opposite to the light guide panel 6 is reflected by the lamp housing 18, and is incident upon the light guide panel 6. The light guide panel 6 uniformly distributes the light incident from the light source 20 thereupon throughout the light guide panel 6, thereby allowing the light to be uniformly incident on the liquid crystal display panel 10.
Furthermore, the reflection plate 4 reflects light emitted from the lower portion of the light guide panel 6, thus supplying the light to the liquid crystal panel 10. The optical sheets 12 include upper and lower diffusion sheets and upper and lower prism sheets. The optical sheets 12 scatter light incident from the light guide panel 6 thereupon so that the light is uniformly distributed to the overall surface of the liquid crystal panel 10. Moreover, the optical sheets 12 refract and concentrate the scattered light to increase surface brightness, and diffuse the light to increase a viewing angle.
To meet the current trends of thin profile and light weight, the LCD devices incorporating these features are developed. Specifically, a liquid crystal display device for a notebook computer is developed to provide enhanced portability. However, the above related art liquid crystal display module has several disadvantages.
The main support and the bottom cover are required in the related art LCD module, thus increasing the total number of steps for fabricating the related art liquid crystal display module. In addition, an overall fabrication time is increased. The bottom cover made of a metal increases the overall production cost. Furthermore, the related art LCD module fabrication processes include connecting the bottom cover and the main support by screw, hence lengthening the fabrication time. Moreover, since the bottom cover and the main support are screw-connected, the portions of the bottom cover and the main support connecting the two parts may wear out. In addition, the use of the bottom cover increases the overall weight and volume of the liquid crystal display module.